Information such as the rotational speed and cooling water temperature of a vehicle engine are displayed on indicators in front of a driver's seat. Torque produced by the engine is not usually displayed or used as data for various control mechanisms such as an automatic transmission. The reason for this is because it is not easy to detect the torque when the vehicle is running.
To correctly detect the torque of the vehicle engine, a bench test using a chassis dynamometer must be carried out. A torque sensor may also be used to precisely detect minimal torsion of shafts interposed in a power transmission system. This torque sensor is expensive.
This applicant has proposed (Japanese Utility Model Application No. 1-102348) an output display unit for calculating and displaying the output or torque of an engine, which is normally operating, according to the intake air quantity and rotational speed of the engine, which si substantially inevitable information required for controlling the fuel supplied to the engine, without using an expensive large scale apparatus.
This output display unit, however, provides a display of figures during deceleration in which the output and basic torque of the engine is actually zero. This happens in some vehicles which lowers the commercial value of the display unit.
This occurs because a small amount of air is supplied to the engine through an anti-afterburning valve (hereinafter referred to as the AB valve), which prevents secondary air and exhaust heat after sudden deceleration from causing afterburning that may cause a temperature increase and explosion in an exhaust system, and a boost control valve (hereinafter referred to as the BC valve), which presents the generation of a large quantity of unburnt gases after sudden deceleration.
Functions of the AB and BC valves will be explained in detail. When a fuel in an intake manifold flows along a wall into a combustion chamber of the engine just before deceleration with a throttle valve completely closed an air-fuel ratio becomes excessively dense, and unburnt fuel is discharged as flows to the exhaust system. This unburnt fuel causes afterburning due to secondary air and exhaust heat, thereby adversely influencing the exhaust system. To prevent this, the AB valve introduces air into the intake manifold at deceleration (a deceleration air-fuel ration correction function). During deceleration with the throttle valve completely closed, a negative pressure in the intake manifold increases to cause a high boost phenomenon. This causes an insufficient compressing pressure, incomplete combustion, increase of unburnt gas (GC) and rise of oil. To prevent this, the BC valve introduces air into the intake manifold to maintain a predetermined negative pressure in the intake manifold during the deceleration (a deceleration negative pressure correction function).
A main object of the invention is to provide an output display unit for a vehicle engine, which displays zeros when AB and BC valves of the engine are active just after deceleration, thereby improving the commercial value of the display unit.
Another object of the invention is to achieve the above main object with use of parameters that can be detected by existing sensors, and correctly display the output and torque of the engine.